Mauro Tadeu Braga da Silva

Controle de Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae) com reguladores de crescimento de insetos

The velvetbean caterpillar, Anticarsia gemmatalis Hubner (Lepidoptera: Noctuidae), is an important soybean pest in Brazil. This study aimed to evaluate growth regulators insecticides. A precision sprayer equipped with 110 02 nozzles, working at a constant pressure of 1 bar and volume of 100 liters per hectare was used to apply the insecticide treatments (diflubenzuron at 15g a.i. per hectare, lufenuron at 7.5 g a.i. per hectare, metoxyfenozide at 21.6g a.i. per hectare and teflubenzuron at 7.5g a.i. per hectare). Applications when plants were 0.90m height, in the R3.1 growth stage, and the number of small larvae was 95, while that of large larvae was 33 per two meters of row. The number of live larvae at 0, 2, 4, 7 and 10 days after application, the defoliation at 15 days after application and grain yield were evaluated. The fastest control of large and small larvae was obtained with metoxyfenozide at 2 days after application. The insecticides diflubenzuron, lufenuron and teflubenzuron efficiently controlled of large and small larvae, but only at 4 days after application. Larval infestations in non-treated plots resulted in significant defoliation and yield losses when compared to plots treated with insecticides.

Reação de cultivares e eficiência do controle químico de pulgões vetores do Barley yellow dwarf virus em trigo

Four experiments were carried out in Cruz Alta, Rio Grande do Sul State, Brazil, during the 2000 growing season, under field conditions, to evaluate the wheat cultivars reaction and efficiency of inseticides to reduce aphid vectors in the Barley yellow dwarf virus (BYDV) incidence and damage. The majority of the aphids collected (75%) was Rhopalosiphum padi (Linnaeus). Other three species of aphids were collected in lower numbers (25%). Only the Fundacep 31 cultivar showed positive reaction to sorological test ELISA, confirming the presence of BYDV-PAV, BYDV-MAV and BYDV-SGV viral species. Cultivars showed different responses, being classified as resistant (Fundacep 30, Fundacep 36 and Fundacep 37) and susceptible (Fundacep 31). Seed treatment with imidacloprid and thiamethoxam in the dosage of 24.5g 100kg of seed-1, were effective to control BYDV aphid vectors, and these treatments were better than conventional 3 foliar sprays with chlorpyriphos. Dosages over 8.5g 100kg of seed-1 of imidacloprid and thiamethoxam avoided reduction in grain yields in wheat caused by the complex aphids-BYDV.

Níveis de desfolha na fase reprodutiva da soja, cv. Ocepar 14, sobre dois sistemas de cultivo

This study aimed to evaluate the defoliation levels under reproductive stages, of soybean cv. Ocepar 14, over no-tillage and conventional tillage systems. Two experiments were conducted, during the 1998/99 growing season, in Santa Maria, in the State of Rio Grande do Sul, Brazil. The defoliation levels were 0, 33, 67 and 100%. Total defoliation decreased grain yield significantly when performed at R3, R4, R5 and R6 stages in both no-tillage and conventional tillage. Total defoliation was more prejudicial to yield at R4 in no-tillage, while R4 and R5 were more sensitive to full in conventional tillage. Defoliations of 33 and 67% decreased grain yield only when applied at R3 stage in the no-tillage system. In the conventional tillage, only defoliation of 67% caused significant reductions on yield in R5 stage. There was no difference between soil tillage systems in the percentage of yield reduction promoted by any of the evaluated defoliation levels.

NÍVEL DE CONTROLE DE Diloboderus abderus EM AVEIA PRETA, LINHO, MILHO E GIRASSOL

O estudo aqui relatado foi conduzido nas safras agricolas de 1991 e 1992, em Cruz Alta, no Rio Grande do Sul. O objetivo foi avaliar o efeito de diferentes niveis de infestacao de Diloboderus abderus Sturm, 1826 (Coleoptera: Melolonthidae) em aveia preta (Avena strigosa L.), em linho (Linum usitatissimum L.), em milho (Zea mays L.) e em girassol (Helianthus annuus L.), no sistema de plantio direto. O aumento do numero de larvas/m2 propiciou a ocorrencia de danos e, em consequencia, a diminuicao da populacao de plantas, da massa seca da parte aerea e da produtividade. Os niveis de controle obtidos foram variaveis dependendo da cultura. Com base nos danos produzidos pelo inseto, sugerem-se os niveis de controle de 12 larvas/m2 em linho, de 10 larvas/m2 em aveia preta, de 0,5 larva/m2 em milho e de 0,4 larva/m2 em girassol, como indicador para tratamento de sementes destas culturas com inseticidas.

CONTROLE DE LARVAS DE Diloboderus abderus COM INSETICIDAS EM TRIGO

The larva of Diloboderus abderus Sturm (Coleoptera: Melolonthidae) is an important wheat (Triticum aestivum L.) pest under no-till system in the Southern region of Brazil. This study aimed to evaluate insecticides applied as seed treatment (fipronil and thiamethoxam) and in soil pulverization (chlorpyriphos and lambdacyhalothrin). The effectiveness of the insecticides were assessed by determining the number of larvae in the soil at 30, 60 and 90 days after emergence, the plant biomass at 90 days after emergence and the grain yield. Significant negative correlations were obtained between doses of fipronil and thiamethoxam with number of larvae. Significant positive correlations were observed between doses of fipronil and thiamethoxam with plant biomass and grain yield. Larvae infestations in non-treated plots caused significant yield losses when compared to plots treated with insecticides. Increasing control of larvae with insecticides increased the crop yield. It is concluded that chlorpyriphos (960 and 1200g a.i./ha) and lambdacyhalothrin a 25g i.a./ha (EC formulation), in soil pulverization, were efficient in reducing larval population and maintaining grain yields. Additional studies with thiamethoxam, fipronil and lambdacyhalothrin (CS formulation) are suggested to determine most efficient technical and economical dosages of these products to control D. abderus larvae in wheat.

Tamanho e número de unidades de amostra de solo para amostragem de larvas de Diloboderus abderus (Sturm) (Coleoptera: Melolonthidae) em plantio direto

The study was carried out in a black oat (Avena strigosa) field cultivated under the no-tillage system in an Oxissol (Dark Red Latosol) with clay texture, in the county of Cruz Alta, Rio Grande do Sul State, to determine the size and number of soil samples for 3rd instar larvae of Diloboderus abderus (Sturm). Considering the average number of larvae/m2, time required for sample extraction, and the relative net precision, the sample unit 25 x 25 cm dug to a depth of 30 cm yielded the best result. Results indicated a great heterogenicity in the distribution of the larvae; 67 (with error of 25% of the mean) and 419 (with error of 10% of the mean) sample units were necessary to give an acceptable estimate of the larval population.

Comportamento de Sternechus subsignatus (Boheman) em dez espécies vegetais de verão para rotação de culturas ou cultura armadilha no plantio direto

The development of Sternechus subsignatus (Boheman) (Coleoptera. Curculionidae) was evaluated on ten crop species under natural conditions under no-tillage system for three years and infested with the insect Soybean was the Summer crop continously cultivated in the area. Number of attacked plants, oviposition, number and weight of larvae and number of adults emerged were the parameters evaluated. The insect reproduced and developed in bean (Phaseolus vulgaris L), grandull (Cajanus cajan L.), dolichos (Dolichos lablab L.) and soybean (Glycine max L.) and not in bengal hemp (Crotalaria juncea L ), sunflower (Helianthus annuus L.), millet (Pennisetum americanum Leek), corn (Zea mays L.), black velvet bean (Stizolobium aterrimum Piper et Tracy) and sorghum (Sorghum bicolor L.) did not complete lhe life cycle Results indicated that P. vulgaris, C. cajan, D. lablab and G. max increased insect populatron but, a reduction was observed on C. juncea, H. annuus, P. americanum, Z. mays, S. aterrimum and S. bicolor. The first four related species are the preferred hosts and may be used as trap crops. The other six species did not host the insect, decreasing its populations and thus being ideal to be included in Summer crop rotafion systems to subslitute soybean monocropping under no-tillage.

Aspectos biológicos de Sternechus subsignatus em soja no sistema plantio direto

Biological aspects of Sternechus subsignatus Boheman (Coleoptera: Curculionidae) were investigated in commercial fields cultivated to soybean (Glycine max L.) under no-tillage system, in Rio Grande do Sul State, from November 1989 to December 1991. S. subsignatus showed one generation a year, with the stages occurring in well defined dates: adults were found form December to March, eggs and larvae in the plants from December to April, larvae in the soil from February to November and pupae and adults in the soil from September to December. The larval stage, in the soil, was the longest period of the life cycle. The duration stage of adults females and males in the plants was 112.5 and 62.9 days, respectivelly. The average number of eggs per female was 158.4 and egg viability was the 89.9%.

Efeito de diferentes métodos de preparo do solo na infestação e danos de Sternechus subsignatus (Boheman) em soja

Sternechus subsignatus (Boheman) is a curculionid occurring in some fields of the traditional soybean production area in southern Brazil. During the 1990/91 growing season, in Cruz A1ta - RS, in an Oxissol (Dark-Red Latossol), clay texture, after four years of soybean cultivation under no-till. the effect of the following soi1 tillage methods on the insect infestation and damage were evaluated: T1) NT = no-till. T2) CT + NT = conventional tillage in July and no-till after October; T3) N T + CT = no-till until July and conventional tillage after October; T4) CT = conventional tillage in July and October. Results demonstrated that the soil tillage methods influenced the establishment and activity of S. subsignatus and, in consequence, the productivity of soybean plants decreased in the soil under no-till and increased in the soil under conventional tillage (plowed and disk arrowed).

Influência da rotação de culturas na infestação e danos causados por Sternechus Subsignatus (Boheman) (Coleoptera: Curculionidae) em plantio direto

The corn and soybean crop rotation on Sternechus subsignatus (Boheman. 1836) infestation and damage under notillage was evaluated in the field in the county of Cruz Alta, Rio Grande do Sul State. Brazil. The results indicated that adult infestation. active larvae and hibernating larvae, and that the percent damage of soybean plants attacked and dead, were significantiy lower in the corn-soybean crop rotation in relation to soybean under monocultural system. Soybean in rotation with corn showes significant more grain productivity than soybean under monocultural system. It was concluded that the corn-soybean rotation is an important tool for the management of S. subsignatus in infested areas due to the fact that the insect neither feed nor perform oviposition on corn plants, thus reducing its population.